1. Field of the Invention
The present invention relates to an interchangeable lens that transmits suitable aberration correction data for digital aberration correction to a camera body in accordance with the type of the camera body or other conditions.
2. Description of the Related Art
In camera systems such as color digital still cameras and video cameras, a color image is reproduced by superimposing images of R (red), G (green) and B (blue) channels. When an object image is imaged on an image pickup element through a lens, a registration error and distortion occur. One of the causes thereof is aberration of the lens, and in particular lateral chromatic aberration and distortion do matter.
Various methods of electrically correcting lateral chromatic aberration and distortion have been conventionally developed. For example, Japanese Patent Application Laid-Open No. 2000-138944 discloses a correction method in which the positions of the pixel outputs of color components that involve registration errors or color registration errors between channels are changed.
Japanese Patent Application Laid-Open No. S61-225988 directed to a data transfer method for an electronic still camera or video camera that uses an interchangeable lens discloses a camera apparatus that is adapted to identify the model number or type of a lens and reads precise correction data suitable for the model number or type of the lens.
Furthermore, Japanese Patent Application Laid-Open No. S62-194787 discloses a camera that uses a lens having a built-in extender function in which a distortion correction amount is changed between when the lens extender is used and when it is not used.
In the systems like those disclosed in Japanese Patent Application Laid-Open No. S61-225988 and Japanese Patent Application Laid-Open No. S62-194787 in which correction data is changed according to the type of the lens or the condition of use thereof, the correction data sent out from the lens is changed or the correction data to be used is selected from among a sets of correction data the camera body has, when the optical system is changed. In such systems, however, no consideration is given to situations in which one interchangeable lens is to be mounted on a plurality of different camera bodies as is the case with lenses for broadcasting cameras or situations in which one interchangeable lens is to be mounted on a camera body in different shooting conditions or in different shooting modes.
Furthermore, broadcasting cameras may have different required resolutions such as high definition (HD), standard definition (SD) and a resolution for cinema. FIG. 16 shows lateral chromatic aberration associated with camera characteristics A and B. Characteristics for the respective colors may vary depending on the mode and type of the camera even if the same lens is used. Accordingly, it is necessary in broadcasting image pickup systems to taking into consideration situations in which the same lens is mounted on different types of cameras or situations in which the same type of camera is used for shooting in different shooting conditions or different shooting modes.